Artist Risa Puno recently completed her interactive mosaic sculpture Common Ground for Rufus King Park in Jamaica Queens, NYC, and the project is a great example for discussing materials and methods for mosaic table tops.
No Plywood Backers Outdoors
Plywood is never an acceptable backer for outdoor mosaic table tops.
Humidity in outdoor air can cause plywood to swell, contract, and warp, and even if the displacement is too small to be noticed, it can still cause grout to crack and tiles to pop off. Once grout has hairline cracks, moisture can penetrate underneath, and then there isn’t any hope for the mosaic lasting after that happens.
If you have a wooden table that you want to mosaic for outdoors, then attach a piece of 1/4-inch concrete backer board over the top of the wood and mosaic on that.
Seal your finished outdoor mosaic with a tile and grout sealer and reseal it each fall. Silicone-based gout sealers are wipe-on-wipe-off and easy to apply. Most of the work is buffing off the excess so that the surfaces are slippery. Continue reading